1. Field of the Invention
The present invention is related to frame structures used in press assemblies and is particularly related to tie rod and compression member frame structures which when employed in the translation of high pressure results in ultra high pressure on the tooling apparatus.
2. Discussion of the Prior Art
Press assemblies using tie rods and compression members (generally known as prestressed tie rod press assemblies) are often employed in many press applications. In such assemblies, the compression members are preloaded to a high percentage of the rated capacity of the press, normally above 100 percent, so that, when the assembly is under load, both the stretch of the vertical members and cyclical fatigue are reduced, resulting in greater stability. Preloading of the assembly is generally accomplished by heating the tie rods through various means such as calrods. While the tie rods are heated and therefore expanded in length, the tie rod nuts are tightened. Upon cooling, the tie rod is preloaded in tension while the compression member is preloaded in compression.
Such characteristics can beneficially be employed in very high pressure applications such as, for example, the compacting of carbonaceous materials into extremely hard products, i.e. diamonds used in various industrial apparatus. Extremely high pressures with concomitant high temperatures introduced by passing an electric current through the material being compacted are necessary in the manufacture of diamonds, the pressures exceeding 1,000,000 p.s.i. Since normal steels used as tooling will fail under this load, it is necessary to use materials with an extremely high Young's Modulus, such as tungsten. Tungsten, like other materials with a high Young's Modulus, characteristically has a poor bending ability. At such high operating conditions, weaknesses in the tool structure due to material defects or fatigue become serious problems and, literally, explosions may occur under an improperly applied load. To protect operating personnel, the entire press assembly must be surrounded by an enclosure, generally fabricated from heavy gauge steel sheet or plates.
The configuration of the assembly affects the safety, accessibility, method of guiding the moving members, structural space requirements, and the total weight of the press structure. The weight requirements needed for high pressure applications obviously detrimentally affect the economics. With high pressure applications, it is additionally necessary to ensure that the moving press platen is precisely guided while it moves the high pressure tooling apparatus to a position where pressure will be applied by holding the tooling apparatus substantially on the central vertical axis of the press assembly. Upon application of pressure, it is important that reactionary loads from the press assembly are not transferred to the apparatus which would tend to induce a shift in position of the high pressure tooling apparatus, thereby resulting in transverse loads on the tooling apparatus and their possible premature failure.
It is, therefore, a paramount object of the present invention to provide for a press assembly, particularly effective in high pressure applications, having reduced weight and space requirements, while maintaining its high safety standards. Another, but equally important, object is to minimize the potential error of tooling apparatus location at the point of, but prior to, application of pressure by reducing the horizontal guiding span length. Still another, but equally important objective, is to maintain the horizontal span of the tooling apparatus working space, even while reducing the guide span of a press assembly which has tie rods and compression members. Still another additional objective is to reduce the relative square footage of safety shrouding, while maintaining or improving the quality of safety shrouding.